This invention has been invented in view of the following disadvantages of conventional articles. The incandescent lamps in the lamp set used in conventional advertising board, decoration and other applications were in paralled connection and its power supply was AC power source. Thus, the power distributor was a necessity to work out the flickering effect for those incandescent lamps in parallel connection. But the cost is high and engineering is not convenient. Also, there are lamp sets for decoration (such as C-7, C-9) with ability of being fully dark and light (i.e. "flickering") only when the bi-metal switch applied to connect and disconnect the power source was in action. The expected flickering effect (being fully dark and light) of lamp set (C-7/C-9) is not satisfactory because of the faiure of full on/off of the bi-metal switch. Besides, the kind of flickering variety that it offers is only one. With this invention, however, a number of flickering varieties is expected and those defects of convention ways are no longer existing.